The four cops ditch their sunglasses for flashlights as they begin trekking through a maze of graffiti-filled flood channels under the streets of La Habra.

They’re looking for homeless people to issue a warning:

A potentially monstrous El Niño-fueled winter is just around the corner, and people living in the tunnels and channels need to move to safer ground – or face the grim possibility of being swept away to their deaths.

The joint effort of the Fullerton and La Habra PDs on Wednesday followed a similar operation last Friday by homeless liaison officers with the FPD to clear several tunnels and channels in their city.

“We let them (the homeless) know they’re not supposed to be there and try to get them to voluntarily comply and relocate,” said FPD Cpl. Dan Heying, one of four officers assigned full time to the FPD’s Homeless Liaison Unit, a model among law enforcement agencies in Orange County and beyond.

The two recent channel-clearing missions weren’t about handing out tickets, although those living in underground encampments can be cited for misdemeanor trespassing.

Rather, the missions were about preventing the loss of human life and steering the homeless to resources such as sober-living homes and shelters.

The four visited three sites in La Habra, finding several encampments but only one person in a channel.

They found one man living in a covered trash collection area behind a business.

The officers encounter a range of emotions when they tell the homeless living underground to relocate.

“They range from uncooperative to frustrated and irritated because they don’t know where else to go,” Heying said.

“One guy we met (last week) had been homeless for 10 years and living in tunnels for about three years, and his reaction was, ‘Hey, I’m an adult. I know what to do when it rains.’”

The officers’ first stop Thursday was a drainage canal under Imperial Highway.

A Modelo beer bottle.

An empty pack of Marlboro cigarettes.

A hockey puck.

The debris strewn throughout this damp and dank world of tunnels is random.

“The people living down here don't like the taggers,” one officer said of the many empty cans of spray paint lying in what, on Thursday, was a modest stream of water.

That stream suddenly could swell into a dangerous rush of water when the heavy rains come --- which is why over the next few weeks, FPD and La Habra PD officers will be making regular sweeps of the tunnels and channels.

“Firm but fair,” Heying said of his approach to the homeless living in flood channels. “We’ve got to be fair to them because they’re in a tough spot, but we also have to enforce the laws when needed.”

Before hitting a tunnel underneath Imperial Highway at Beach Boulevard, the officers notice a man living in an enclosed area for large trash bins.

The lock had been cut.

“Are you lined up with any (social) services?” Garcia asks a 51-year-old man sitting besides a sleeping bag and a bike and a shopping cart full of trash and other items.

A faint whiff of urine permeates the enclosed space.

The man tells Garcia he’s been living next to the trash bins for a couple of days and that he suffers from bipolar disorder and has been off his medication or a while.

Garcia suggests he make an appointment with a doctor to get back on his meds.

“That’s what I’m going to do,” the man tells Garcia.

The cop searches his backpack and finds an unopened syringe.

The man admits to using heroin but said he’s been clean a week.

Garcia doesn’t cite him because the syringe still is sealed in a package.

The man says he’s open to contacting a sober living home; he owns a cell phone.

The four officers move on.

In the tunnel under Imperial Highway, the officers discover an encampment for several people.

But no one’s home.

They talk to a man at the far end of the tunnel who says he’s just passing through.

On the walls of the underground encampment are touches of home.

Broken shards of mirrored glass are glued to the walls.

A Gucci ad torn from a magazine serves as a poster.

Someone glued a cover of a light switch to the concrete wall – an imaginary source of light in this world of darkness.

“The people who live down here,” Lucarevic says, “are real resourceful. And they do what they can to make it look as much as a home as possible.”

But it’s not a place anyone should ever have to call home.

But many do.

And the heavy rains are coming.

So the officers will head out again soon into a world of darkness most of Orange County never sees, in the hopes of getting the word out --- and perhaps helping someone take the steps they need to begin crawling back into the light of day.